Submarine torpedo ejection pumps include long, large diameter cylinders through which a piston travels, to eject torpedos during launch. When a submarine comes into a shipyard for periodic overhaul, the ejection pump cylinders are inspected and repaired to maintain their maximum functional efficiency. The cylinders are inspected for roundness and straightness and repaired as required to conform to specified geometric tolerances. Periodic maintenance is essential to prevent the piston from binding in the cylinder. Because the cylinder is welded into the structure of the submarine, it is not possible to remove it from the ship for repairs. Making the need clear for an apparatus which can be used on site at a shipyard for machining the interior surfaces of defective torpedo ejection cylinders.